Techniques for improved wireless energy transmission efficiency

ABSTRACT

Techniques for improving efficiency of wireless power transfer to shunt-based receiver are provided. In an example, techniques can optimize wireless power transfer by comparing instantaneous peak voltage of a transmit coil of a wireless power transmitter to an average peak voltage of the transmit coil, and then, based on the comparison, adjust a setpoint of the wireless power transmitter to a more efficient level.

CLAIM OF PRIORITY

This application claims the benefit of priority to Li et al., U.S.Provisional Patent Application Ser. No. 62/901,049, titled, TECHNIQUESFOR IMPROVED WIRELESS POWER TRANSMISSION EFFICIENCY, filed Sep. 16, 2019and hereby incorporated by reference herein in its entirety.

TECHNICAL FIELD

This disclosure relates to wireless energy transfer, and moreparticularly, to techniques for more efficient wireless energy transfer.

BACKGROUND

Wireless energy transfer techniques such as for wireless charging isfacing increasing demands for ministration as such techniques eliminatesthe need for cables or any exposed connectors on a device. Forefficiency, some wireless transfer systems are arranged in a closed loopto allow the transmitter to actively adjust its output power based onthe demands of its receiver and coupling coefficient between the twosides. Without such an arrangement, the receiver dissipates the extrapower in the form of heat, impacting the user experience and posing athreat to the health of the battery. Digital communication from thereceiver to the transmitter is usually used to close this loop, but itadds complexity in overall design, and increases the size of theapplication.

BACKGROUND

Techniques for improving efficiency of wireless energy transfer areprovided. In an example, a circuit for optimizing wireless energytransfer can include a comparator circuit configured to receive a firstrepresentation of an instantaneous peak voltage of a transmit coil of awireless power transmitter, to receive a second representation of anaverage peak voltage of the transmit coil and to provide an outputrepresenting a result of a comparison of the first representation withthe second representation, and a transistor configured to adjust asetpoint of the wireless power transmitter in response to an output ofthe comparator.

This section is intended to provide an overview of subject matter of thepresent patent application. It is not intended to provide an exclusiveor exhaustive explanation of the invention. The detailed description isincluded to provide further information about the present patentapplication.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, various embodiments discussed in the presentdocument.

FIG. 1 illustrates generally an example wireless energy transfer system.

FIG. 2 illustrates generally a block diagram of an example energytransmit system including an energy transmitter circuit and transmitcoil.

FIG. 3 illustrates generally an alternative example architecture of anexample energy transmit system.

FIG. 4 illustrates generally an alternative example energy transmitsystem.

FIGS. 5A and 5B illustrates generally an example of the response of anenergy transmit circuit as described above with respect to the examples,of FIGS. 1-4 as the power demand of the energy receiver circuit fallsover time.

FIG. 5C illustrates generally an example of the response of an energytransmit circuit as described above with respect to the examples, ofFIGS. 1-4 as the power demand of the energy receiver circuit rises overtime.

FIG. 6 illustrates generally a flowchart of an example method ofoperating an energy transmit circuit of wireless energy transfer systemaccording to the present subject matter.

DETAILED DESCRIPTION

The present inventors have recognized techniques for closing the loopbetween the wireless energy receiver and the wireless energytransmitter, without the complexity of employing digital communicationacross the wireless link. In some examples, the wireless energytransmitter, or energy transmitter may be referred to as a wirelesspower transmitter or a power transmitter. Compared to convention digitalcommunication methods the present subject matter can provide lesscomplexity, external component count and smaller overall footprint onthe receiver device. FIG. 1 illustrates generally an example wirelessenergy transfer system 100. In certain examples, the wireless energytransfer system 100 can include energy transmitter circuit 101, a powerreceiver circuit 102, a transmit coil 103 and a receiver coil 104. Thewireless energy transfer system 100 can also include power supply 105coupled to the energy transmitter circuit 101 during operation and aload 106 coupled to the power receiver circuit 102 during operation.During operation, when transmit and receive coils 103, 104 are inproximity to each other, the energy transmitter circuit 101 can use thepower supply 105 to induce a varying magnetic field via the transmitcoil 103. The varying magnetic field can induce current in the receivercoil 104 and the power receiver circuit 102 can harvest power from theinduced current. As such, the wireless energy transfer system 100 cantransfer power across the air gap between transmit and receive coils103, 104.

In certain examples, the load 106 can be a power storage device such asa battery or a capacitor. In such an example, the power storage devicecan be a part of a mobile electronic device that may also include thepower receiver circuit 102 and the receiver coil 104. In some examples,the load 106 can be an electronic circuit other than a storage device.In some examples, the load 106 can include both an electronic circuitand a storage device. In certain examples, the amount of power consumedby the load 106 can vary. Many conventional energy transfer systems areconfigured to provide power at one level at all times. When the load 106demand is less that the power available from the energy transmittercircuit 101, the power receiver circuit 102 shunts the receiver coilcurrent to prevent the output voltage from rising too high anddissipates some or all the extra power as heat. The present inventorshave recognized that the voltage characteristics of the transmit coil103 change when the power receiver circuit 102 shunts current of thereceiver coil 104. In certain examples, the voltage characteristic ofthe transmit coil 103 can be monitored by the energy transmitter circuit101 and used to adjust the amount of power provided by the energytransmitter circuit 101 via the transmit coil 103 so as to provide moreefficient energy transfer for a varying load and to reduce thermalbuild-up in the power receiver circuit. In certain examples, theimprovements can be accomplished without employing a digitalcommunication scheme between the energy transmit circuit and the powerreceiver circuit.

FIG. 2 illustrates generally a block diagram of an example energytransmit system 230 including an energy transmitter circuit 201 andtransmit coil 203. In certain examples, the transmit coil 203 can bepart of a series resonant tank 213 that can include a transmit capacitor223. In certain examples, a switch output (SW) of the energy transmittercircuit 201 can selectively couple the series resonant tank 213 to thepower rails (VIN, GND) to induce the magnetic field necessary for energytransfer. In certain examples, a feedback circuit 210 can be coupled toan intermediate node of the series resonance tank 213 to monitor avoltage of the series resonant tank 213 and provide a feedback signal(FB) to the energy transmitter circuit 201 that can be used tocontinuously modulate a duty cycle of the switch output (SW).

FIG. 3 illustrates generally an alternative example architecture of anexample energy transmit system 330. FIG. 3 also provides a more detailedrepresentation of an example feedback circuit 310. In certain examples,the energy transmit system 330 can include an energy transmitter circuit301, a resonance tank 313 including a transmit coil 303 and a transmitcapacitor 323, and the feedback circuit 310. In certain examples, theenergy transmitter circuit 301 can include a full bridge switchingcircuit that can include two switch outputs (SW1, SW2) for selectivelycoupling each end of the resonance tank 313 to the power rails (VIN,GND). Such full-bridge power transmitter circuits can typically provideup to twice as much energy transfer compared to the half bridgearchitecture as shown in FIG. 2. In certain examples, a full bridgepower transmitter circuit can be used in a half bridge mode orarchitecture.

In certain examples, the feedback circuit 310 can include aunidirectional pass device such as a diode 331 to sample a voltage of anintermediate node of the resonance tank 313. The feedback circuit 310can include a voltage divider 332, and average network 333, a comparator334, a switch 335, a current limiter such as a current limit resistor336 and a storage capacitor 337. The voltage divider 332 can provide ascaled representation of the instantaneous peak voltage of the resonancetank 313 and can include two or more resistors coupled in series betweenthe rectified intermediate node and ground. The average network 333 caninclude a current limit resistor and an averaging capacitor coupled tothe voltage divider 332. The average network 333 can provide a scaledrepresentation of an average peak voltage of the intermediate node ofthe resonance tank 313. The comparator 334 can compare the instantaneouspeak voltage provide by the voltage divider 332 with the average peakvoltage provided by the average network 333 and can provide a binaryresult of the comparison. The output of the comparator 334 can control aswitch 335 coupled to the feedback node (FB) of the energy transmittercircuit 301.

The structure of the feedback circuit 310 as discussed above is intendedto provide pulses at the output of the comparator 334 when the receiverpower circuit shunts the current of the receiver coil. For example, whenthe receiver power circuit receives too much power from the energytransmitter circuit 301, the receiver power circuit will momentarilyshunt the current of the receiver coil to prevent the output voltagefrom rising too high and to dissipate some or all of the excess power asheat. The frequency of the shunt events can increase as the differencebetween low power demand of the load and the wireless power receivedincreases. When the power receiver circuit shunts current of thereceiver coil, the linkage between the transmit coil 303 and thereceiver coil changes such that the voltage at the intermediate node ofthe resonance tank 313 climbs or spikes during the shunt event. Thespikes, or peaks in the instantaneous voltage of the intermediate nodeof the transmit resonance tank 313 of the energy transmitter circuit 301can become greater than the average peak voltage of the intermediatenode of the transmit resonance tank 313. At such times, the output ofthe comparator 334 can change states which can generally result ingeneration of a pulse at the output of the comparator 334. In certainexamples, the pulse can activate or trip the switch 335.

When the switch 335 is tripped, the feedback node (FB) can be pulledlow. When the feedback node (FB) is pulled low, a duty cycle of theswitching scheme of the energy transmitter circuit 301 can be adjustedto reduce the wireless energy transfer provided by the transmitresonance tank 313. In certain examples, the current limit resistor 336and storage capacitor 337 can be used to adjust a response of the dutycycle change. In certain examples, internal to the energy transmittercircuit 301, the feedback node (FB) can be coupled to a pull-up circuitsuch as a pull-up resistor. As such, when the feedback node (FB) is notbeing pulled low by the switch 335, the feedback node (FB) can be pulledup to a voltage level indicative of a maximum duty cycle, or maximumenergy transfer set point, for the energy transmitter circuit 301.

FIG. 4 illustrates generally an alternative example energy transmitsystem 430. In certain examples, the energy transmit system 430 canincludes an energy transmitter circuit 401, a transmit resonance tank403, and a feedback circuit 410. The energy transmitter circuit 401 caninclude switching logic 440 that includes a full bridge and two switchoutputs (SW1, SW2) coupled to the transmit resonance tank 413. Incertain examples, the feedback circuit 410 can include a unidirectionalpass device such as a diode 431 to sample a voltage of an intermediatenode of the resonance tank 413. The feedback circuit 410 can include avoltage divider 432, and average network 433, a comparator 434, a switch435, a current limit 436 and a storage capacitor 437. The feedbackcircuit s operates as discussed above with respect to the example ofFIG. 3.

In certain examples, the energy transmitter circuit 401 can include acontroller 441. The controller 441 can include a digital processor,control logic, control circuitry, or combinations thereof. In certainexamples, the controller 441 can include a register 442, adigital-to-analog converter (DAC) 443, and a pull-up resistor 444 to seta command signal for a duty cycle of the switching logic 440. Theregister 442 can define a maximum duty cycle and can be programmable incertain examples. The value of the register 442 can be converted to ananalog signal such as a voltage by the DAC 443 and can be partiallybuffered from a setpoint terminal 445 by the pull-up resistor 444. Asdiscussed above, the feedback circuit 410 can pull the setpoint terminal445 lower by activating the switch 435 of the feedback circuit 410. Incertain examples, activation of the switch 435 can take the form ofcycling the switch 435 whenever the power receiver shunts current of thereceiver coil. In certain examples, the voltage divider 432 can providean additional, second feedback signal (FB2). In certain examples, theadditional, optional, second feedback signal (FB2) can be used to by thecontroller 441 to adjust the value of the register 442 via a searchroutine with a much lower loop update than the closed loop controlprovided by the first feedback signal (FB). In some examples, the secondfeedback signal (FB2) can be used to provide over-voltage protection.

In certain examples, the energy transmitter circuit 401 can include thecircuits for generating the resonant driving frequency discussed inLisuwandi, U.S. Pat. No. 9,524,824 which is hereby incorporated byreference herein in its entirety. The techniques for generating theresonant driving frequency can assist in improving the response of theenergy transmitter circuit 401 when combined with the techniques foradjusting the duty cycle based on the first feedback signal (FB)discussed above. FIGS. 5A and 5B illustrate generally an example of theresponse of an energy transmit circuit as described above with respectto the examples, of FIGS. 1-4 as the power demand of the power receivercircuit falls over time. FIGS. 5A and 5B show current demand 501 ofpower receiver circuit, the voltage 502 at the intermediate node of thetransmit resonance tank, and the voltage 503 at the feedback node. Asthe power demand of the energy transmit receiver falls, the energytransmit receiver shunts the current of the receiver coil more oftencreating a high frequency pulse train activating the feedback switchcircuit, that in turn significantly lowers the voltage at the feedbacknode (FB). As the proper balance of energy transmission is reached, theshunting events begin to occur at regular intervals. Because the rate offall of the power demand is so great in FIG. 5A, it is difficult toclearly see the increased frequency of the shunt events andcorresponding drop in the voltage at the feedback node. FIG. 5Billustrates the same drop in power demand as in FIG. 5A in a relativelyexpanded time scale. The expanded time scale clearly shows that as thepower demand of the load falls, the frequency of the shunt eventsincreases and the voltage of the feedback node (FB) falls.

FIG. 5C illustrates generally an example of the response of an energytransmit circuit as described above with respect to the examples, ofFIGS. 1-4 as the power demand of the power receiver circuit rises overtime. FIG. 5C shows current demand 501 of power receiver circuit, thevoltage 502 at the intermediate node of the transmit resonance tank, andthe voltage 503 at the feedback node. As the power demand of the energytransmit receiver rises, the energy transmit receiver does not shunt thecurrent of the receiver coil as often. When the feedback switch is notactivated, the feedback node (FB) is ramped and pulled to a valueindicative of a maximum duty cycle. When the duty cycle adjusts toprovide adequate energy transfer to the power receiver, the shuntingevents begin to occur at regular intervals.

FIG. 6 illustrates generally a flowchart of an example method 600 ofoperating an energy transmit circuit of wireless energy transfer systemaccording to the present subject matter. At 601, a first representationof an instantaneous peak voltage of the intermediate node of thetransmit resonance tank can be received at a comparator of a feedbackcircuit. The transmit resonance tank can include a transmit coil and atransmit capacitor. When the transmit coil is properly excited with anelectrical signal and is in close proximity to a receiver coil of apower receiver circuit, power can be transferred from the transmit coilto the receiver coil to power a load connected to the power receivercircuit. At 603, a second representation of an average peak voltage ofthe intermediate node of the transmit resonance tank can be received atthe comparator. At 605, the comparator can compare the firstrepresentation with the second representation. When the power receivercircuit is receiving more power than is required to operate the load,the power receiver circuit can shunt current of the receiver coil toprevent the output voltage from rising too high and to dissipate some orall the extra power via heat. The shunting action can result in avoltage spike in the instantaneous voltage of the intermittent node ofthe transmit resonance tank. Likewise, the first representation canexperience a spike in value that can cause the first representation toexceed the second representation and the output of the comparator cantoggle or create a pulse. At 607, the result of the comparison canadjust a duty cycle of the excitation signal of the transmit resonancetank such that the energy transfer is adjusted to more closely resemblethe power demand of the load. In certain examples, the duty cycle of thetransmit power circuit can be configured to constantly ramp to a higherduty cycle in the absence of the feedback circuit detecting a new shuntevent of the power receiver circuit. In certain examples, efficientoperation of the system is achieved when the shunt events occur atregular, spaced apart intervals.

NOTES

In Example 1, a system can include a wireless power transmitterconfigured to electrically excite a transmit coil with a pulse train totransmit power, the pulse train having a duty cycle, wireless powerreceiver configured to wirelessly receive the power from the wirelesspower transmitter, a load electrically and mechanically coupled to thewireless power receiver and configured to receive power form thewireless power receiver, and a feedback circuit. The feedback circuitcan include a network configured to provide an instantaneousrepresentation of a peak voltage of the transmit coil and an averagerepresentation of the peak voltage of the transmit coil, and acomparator circuit configured to compare the instantaneousrepresentation with the average representation and to provide an outputconfigured to adjust the duty cycle.

In Example 2, the comparator circuit of Example 1 optionally includes acomparator configured to receive the instantaneous representation andthe average representation, and a transistor configured to divertcurrent from a setpoint of the wireless power transmitter in response toan output of the comparator.

In Example 3, the network of any one or more of Examples 1-2 optionallyincludes a first branch configured to provide the instantaneousrepresentation and a second branch configured to provide the averagerepresentation.

In Example 4, the first branch of any one or more of Examples 1-3optionally includes a voltage divider.

In Example 5, the second branch of any one or more of Examples 1-4optionally includes a capacitor.

In Example 6, a first node of the first branch and a first node of thesecond branch of any one or more of Examples 1-5 optionally are coupleddirectly to a supply rail of the wireless power transmitter.

In Example 7, a second node of the first branch of any one or more ofExamples 1-6 optionally is configured to electrically couple with thetransmit coil.

In Example 8, a second node of the second branch of any one or more ofExamples 1-7 optionally is coupled to an intermediate node of the firstbranch.

In Example 9, the system of any one or more of Examples 1-8 optionallyincludes a diode configured to couple the network with the transmitcoil.

In Example 10, a circuit for optimizing wireless power transfer caninclude a comparator circuit configured to receive a firstrepresentation of an instantaneous peak voltage of a transmit coil of awireless power transmitter, to receive a second representation of anaverage peak voltage of the transmit coil and to provide an outputrepresenting a result of a comparison of the first representation withthe second representation, and a transistor configured to adjust asetpoint of the wireless power transmitter in response to an output ofthe comparator.

In Example 11, the circuit of any one or more of Examples 1-10optionally a passive network configured to electrically couple with thetransmit coil, the passive network configured to provide the firstrepresentation and the second representation.

In Example 12, the passive network of any one or more of Examples 1-11optionally includes a first branch configured to provide the firstrepresentation and a second branch configured to provide the secondrepresentation.

In Example 13, the first branch of any one or more of Examples 1-12optionally includes a voltage divider, and the second branch of any oneor more of Examples 1-12 optionally includes a capacitor.

In Example 14, a first node of the first branch and a first node of thesecond branch of any one or more of Examples 1-13 optionally are coupleddirectly to a supply rail of the wireless power transmitter.

In Example 15, a second node of the first branch of any one or more ofExamples 1-14 optionally is configured to electrically couple with thetransmit coil.

In Example 16, a second node of the second branch of any one or more ofExamples 1-15 optionally is coupled to an intermediate node of the firstbranch.

In Example 17, the circuit of any one or more of Examples 1-12optionally include a diode configured to couple the passive network withthe transmit coil.

In Example 18, a method of adjusting a wireless power transfer caninclude receiving a first representation of an instantaneous peakvoltage of a voltage of a transmit coil, receiving a secondrepresentation of an average peak voltage of the voltage of the transmitcoil, comparing the first representation with the second representationto provide a first comparison, and adjusting a duty cycle of anexcitation signal of the transmit coil based on the first comparison.

In Example 19, the method of any one or more of Examples 1-18 optionallyincreasing the duty cycle of the excitation signal between comparisonsof the first representation and the second representation.

In Example 20, the adjusting the duty cycle of any one or more ofExamples 1-19 optionally includes reducing the duty cycle.

In Example 21, a system can include a load configured to receive powerfor operation, the load including a wireless energy receiver configuredto receive first energy wirelessly via a receive inductor and to shuntthe receive inductor to dissipate excess wireless energy, wherein thepower is derived from the first energy, and a wireless energy transfermanagement circuit for managing wireless energy transfer from a wirelessenergy transmitter to the wireless energy receiver. The wireless energymanagement circuit can include a wireless energy transmitter including atransmit inductor, and a transmit energy control input configured toadjust a level of wireless energy transfer by the wireless energytransmitter in response to an indication, at the transmit inductor, ofan occurrence of shunting of the excess wirelessly energy.

In Example 22, a wireless energy transfer management circuit formanaging wireless energy transfer from a wireless energy transmitter toa wireless energy receiver having incoming wireless energy shuntingcapability can include a wireless energy transmitter including atransmit inductor, and a transmit energy control input configured toadjust wireless energy transfer by the wireless energy transmitter inresponse to an indication, at the transmit inductor, of an occurrence ofshunting of wirelessly transferred energy away from a load that iselectrically coupled to a wireless energy receive inductor of thewireless energy receiver.

In Example 23, the wireless energy transmitter of any one or more ofExamples 1-22 optionally includes a receiver shunt detector configuredto provide the indication in response to a voltage spike on the transmitinductor.

In Example 24, the wireless energy transmitter of any one or more ofExamples 1-23 optionally is configured to incrementally increase a dutycycle of an excitation signal of the transmit inductor.

In Example 25, the receiver shunt detector of any one or more ofExamples 1-24 optionally includes a comparator configured to generatethe indication.

In Example 26, the wireless energy transmitter of any one or more ofExamples 1-25 optionally is configured reduce the duty cycle in responseto a pulse output of the comparator received at the transmit energycontrol input.

In Example 27, the comparator of any one or more of Examples 1-26optionally is configured to receive a first representation of aninstantaneous peak voltage of the transmit inductor and to receive asecond representation of an average peak voltage of the transmitinductor.

In Example 28, the comparator of any one or more of Examples 1-27optionally is configured to provide a pulse output in response to thefirst representation exceeding the second representation.

In Example 29, the wireless energy transmitter of any one or more ofExamples 1-28 optionally is configured to reduce a duty cycle of anexcitation signal of the transmit inductor in response to theindication.

In Example 30, the wireless energy transmitter of any one or more ofExamples 1-29 optionally is configured to incrementally increase theduty cycle absent the indication of the occurrence of shunting.

In Example 31, a method of operating a wireless power transmitter caninclude transmitting energy to a receiver device using a transmitinductor, detecting a shunt event of the receiver device via a voltagespike on the transmit inductor, and adjusting level of energy transferto the receiver in response to the shunt event.

In Example 32, the method of any one or more of Examples 1-31 optionallyinclude incrementing the level of energy transfer to the receiver deviceabsent detection of a shunt event at the receiver device.

In Example 33, the transmitting energy to the receiver device of any oneor more of Examples 1-32 optionally includes exciting the transmitinductor with an excitation signal having a duty cycle, wherein a higherduty cycle is configured to transmit a higher level of energy comparedto a lower duty cycle.

In Example 34, the detecting a shunt event of any one or more ofExamples 1-33 optionally includes comparing a first representation of aninstantaneous peak voltage of the transmit inductor with a secondrepresentation of average peak voltage of the transmit inductor.

In Example 35, the detecting a shunt event of any one or more ofExamples 1-34 optionally includes providing a pulse output in responseto the first representation exceeding the second representation.

In Example 36, the adjusting the level of energy transfer of any one ormore of Examples 1-35 optionally includes reducing a duty cycle of anexcitation signal of the transmit inductor, wherein a higher duty cycleis configured to transmit a higher level of energy compared to a lowerduty cycle.

In Example 37, the reducing the duty cycle of any one or more ofExamples 1-36 optionally includes biasing a duty cycle setpoint inresponse a pulse representation of the shunt event.

In Example 38, a circuit for optimizing wireless energy transfer to ashunting receiver can include a wireless energy transmitter configuredto excite a transmit inductor with an excitation signal having a dutycycle, means for providing a duty cycle setpoint for the duty cycle,means for detecting a shunt event at the circuit; and means foradjusting the duty cycle setpoint in response to the shunt event.

In Example 39, the means for providing a duty cycle setpoint of any oneor more of Examples 1-38 optionally include a digital-to-analogconverter configured to receive a digital setpoint and to provide ananalog setpoint to the wireless energy transmitter.

In Example 40, the means for adjusting the duty cycle of any one or moreof Examples 1-39 optionally includes a transistor configured to bias anoutput of the means for providing a duty cycle in response to an outputof the means for detecting a shunt event.

In Example 41, the means for adjusting the duty cycle of any one or moreof Examples 1-40 optionally includes a capacitor configured to limit achange of the output of the means for providing a duty cycle.

In Example 42, the means for detecting includes means for comparing aninstantaneous peak voltage of the transmit coil with an average peakvoltage of the transmit coil and means for providing a pulse output whenthe instantaneous peak voltage is greater than the average peak voltage.

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” Such examples can include elements in addition tothose shown or described. However, the present inventors alsocontemplate examples in which only those elements shown or described areprovided. Moreover, the present inventors also contemplate examplesusing any combination or permutation of those elements shown ordescribed (or one or more aspects thereof), either with respect to aparticular example (or one or more aspects thereof), or with respect toother examples (or one or more aspects thereof) shown or describedherein.

In the event of inconsistent usages between this document and anydocuments so incorporated by reference, the usage in this documentcontrols.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In this document, the terms “including” and “inwhich” are used as the plain-English equivalents of the respective terms“comprising” and “wherein.” Also, the terms “including” and “comprising”are open-ended, that is, a system, device, article, composition,formulation, or process that includes elements in addition to thoselisted after such a term are still deemed to fall within the scope ofsubject matter discussed. Moreover, such as may appear in a claim, theterms “first,” “second,” and “third,” etc. are used merely as labels,and are not intended to impose numerical requirements on their objects.

Method examples described herein may be machine or computer-implementedat least in part. Some examples can include a computer-readable mediumor machine-readable medium encoded with instructions operable toconfigure an electronic device to perform methods as described in theabove examples. An implementation of such methods can include code, suchas microcode, assembly language code, a higher-level language code, orthe like. Such code can include computer readable instructions forperforming various methods. The code may form portions of computerprogram products. Further, in an example, the code can be tangiblystored on one or more volatile, non-transitory, or non-volatile tangiblecomputer-readable media, such as during execution or at other times.Examples of these tangible computer-readable media can include, but arenot limited to, hard disks, removable magnetic disks, removable opticaldisks (e.g., compact disks and digital video disks), magnetic cassettes,memory cards or sticks, random access memories (RAMs), read onlymemories (ROMs), and the like.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to allowthe reader to quickly ascertain the nature of the technical disclosure.It is submitted with the understanding that it will not be used tointerpret or limit the scope or meaning of a claim. Also, in the aboveDetailed Description, various features may be grouped together tostreamline the disclosure. This should not be interpreted as intendingthat an unclaimed disclosed feature is essential to any claim. Rather,inventive subject matter may lie in less than all features of aparticular disclosed embodiment. The following aspects are herebyincorporated into the Detailed Description as examples or embodiments,with each aspect standing on its own as a separate embodiment, and it iscontemplated that such embodiments can be combined with each other invarious combinations or permutations.

What is claimed is:
 1. A wireless energy transfer management circuit formanaging wireless energy transfer from a wireless energy transmitter toa wireless energy receiver having incoming wireless energy shuntingcapability, the circuit comprising: the wireless energy transmitterincluding: a transmit inductor; a transmit energy control inputconfigured to adjust wireless energy transfer by the wireless energytransmitter in response to an indication, at the transmit inductor, ofan occurrence of shunting of wirelessly transferred energy away from aload that is electrically coupled to a wireless energy receive inductorof the wireless energy receiver; and a feedback circuit including acomparator configured to provide the indication to the transmit energycontrol input to: (i) reduce a duty cycle of an excitation signal of thetransmit inductor in response to indication of an occurrence ofshunting; and (ii) incrementally increase the duty cycle of anexcitation signal of the transmit inductor absent indication of anoccurrence of shunting.
 2. The circuit of claim 1, wherein the feedbackcircuit is configured to provide the indication in response to a voltagespike on the transmit inductor.
 3. The circuit of claim 1, wherein thewireless energy transmitter is configured to incrementally increase theduty cycle of the excitation signal of the transmit inductor.
 4. Thecircuit of claim 1, wherein the comparator is configured to generate theindication based on a relationship between an instantaneous peak voltageand an average peak voltage at the transmit inductor.
 5. The circuit ofclaim 4, wherein the feedback circuit is configured to reduce the dutycycle of the excitation signal and, in response, the wireless energytransmitter is configured to reduce the wireless energy transfer by thetransmit inductor.
 6. The circuit of claim 1, wherein the comparator isconfigured to receive a first representation of an instantaneous peakvoltage of the transmit inductor and to receive a second representationof an average peak voltage of the transmit inductor.
 7. The circuit ofclaim 6, wherein the comparator is configured to provide a pulse outputin response to the first representation exceeding the secondrepresentation.
 8. A method of operating a wireless power transmitter,the method comprising: transmitting energy to a receiver device using atransmit inductor; detecting a shunt event of the receiver device via avoltage spike on the transmit inductor; and adjusting level of energytransfer to the receiver in response to the shunt event, includingadjusting a duty cycle of an excitation signal of the transmit inductor,wherein the duty cycle is reduced in response to the shunt event and theduty cycle is incrementally increased absent indication of the shuntevent.
 9. The method of claim 8, including incrementing the level ofenergy transfer to the receiver device absent detection of a shunt eventat the receiver device.
 10. The method of claim 8, wherein transmittingenergy to the receiver device includes exciting the transmit inductorwith the excitation signal, wherein a higher duty cycle of theexcitation signal is configured to transmit a higher level of energycompared to a lower duty cycle.
 11. The method of claim 8, whereindetecting a shunt event includes comparing a first representation of aninstantaneous peak voltage of the transmit inductor with a secondrepresentation of average peak voltage of the transmit inductor.
 12. Themethod of claim 11, wherein detecting the shunt event further includesproviding a pulse output in response to the first representationexceeding the second representation.
 13. The method of claim 8, whereinthe adjusting the level of energy transfer includes reducing the dutycycle of an excitation signal of the transmit inductor, wherein a higherduty cycle is configured to transmit a higher level of energy comparedto a lower duty cycle.
 14. The method of claim 13, wherein reducing theduty cycle includes biasing a duty cycle setpoint in response a pulserepresentation of the shunt event.
 15. A circuit for optimizing wirelessenergy transfer to a shunting receiver, the circuit comprising: awireless energy transmitter configured to excite a transmit inductorwith an excitation signal having a duty cycle; means for providing aduty cycle setpoint for the duty cycle; means for detecting a shuntevent at the circuit; means for biasing an output of the means forproviding the duty cycle setpoint in response to an output of the meansfor detecting a shunt event; and means for adjusting the duty cyclesetpoint, wherein the duty cycle is reduced in response to the shuntingevent and the duty cycle is incrementally increased absent the shuntingevent.
 16. The circuit of claim 15, wherein the means for providing aduty cycle setpoint include a digital-to-analog converter configured toreceive a digital setpoint and to provide an analog setpoint to thewireless energy transmitter.
 17. The circuit of claim 15, wherein themeans for biasing the output of the means for providing a duty cyclesetpoint includes a transistor.
 18. The circuit of claim 17, wherein themeans for adjusting the duty cycle setpoint includes a capacitorconfigured to limit a change of the output of the means for providing aduty cycle setpoint.
 19. The circuit of claim 15, wherein the means fordetecting includes means for comparing an instantaneous peak voltage ofa transmit coil of the transmit inductor with an average peak voltage ofthe transmit coil, and means for providing a pulse output when theinstantaneous peak voltage is greater than the average peak voltage.